It is well-known in road pavers to electrically heat the screed with the compacting units, such as tampers, screed plates and pressure bars. These components must be heated to prevent the also heated laying material from adhering to the components. The temperature of the laying material is, in the working state, about 160-185° C. Therefore, heating elements with resistance wire windings are attached to the screed of the road paver and preheat the screed to the required operating temperature prior to the laying operation and maintain the same during the laying operation. The heating elements are here normally supplied with power and voltage by a generator driven by a primary drive, usually a diesel engine. To limit the power input or energy consumption of the screed heating, it is known to operate individual heating elements of different screed segments in a clocked manner, i.e., alternatingly, as is described, for example, in EP 1 036 883 B1. As is shown in EP 1 295 990 A2, the clocking can also take into consideration the temperature of the screed segments. From EP 1 555 348 B1, heating elements comprising a plurality of heating spirals or heating wire windings are moreover known, wherein the heating power of each one of the heating spirals corresponds to the rated heating power of the heating element, thus providing a redundancy in case of a failure of a heating spiral. Moreover, a generator can provide variable electric power due to different engine speeds, as is described in WO 2014/124545 A1.
The above-mentioned variants, however, involve deficiencies in operating the heating elements and the generator with an optimal efficiency and simultaneously optimally utilising the performance of the existing components. In particular during the heating phase of the screed, the demands on the generator and heating elements are different from those during the laying operation. Moreover, screeds in different configurations are known. Apart from road pavers with screeds having a fixed working width, road pavers with screeds of variable working widths are also known. Such screeds usually comprise a basic screed of a fixed size, the dimensions of which may be modified by selectively attaching or detaching broadening parts to be able to provide the respective desired road width. This change of the size also requires adjusting the heating power of the screed heating. U.S. Pat. No. 8,961,064 B2 describes a heating system for a screed with a recognition of the attached broadening parts. Finally, EP 3 075 909 A1 discloses a road making machine with a network in which a portion of a power line is used for data transmission.